The present invention relates generally to a programmed shutter and more particularly to an electronic programmed shutter having an extremely simple construction in which a sector also used as an aperture vane is normally biased in such a direction as the same is closed, the sector is opened by a driving member which is moved at a specified speed, the cooperative relation between the sector and the driving member being released by an electromagnetic device, and the sector is closed under its own characteristic to obtain an exposure suitable for taking a photograph.
In a conventional type of electronic programmed shutter of the type described above, a system has been proposed comprising a sector which is also used as an aperture vane, a first ring having a motive force acting in such a direction as the sector is closed and a second ring having a motive force acting in such a direction as the sector is opened. The second ring has a driving lever thereon for engaging with the first ring and the second ring starts its operation by the release operation. The first ring is operated via the driving lever to open the sector, and the driving lever is operated by an electromagnetic device to interrupt the relation between the second ring and the first ring and thereby the sector is closed by the self-motive force of the first ring.
However, in such a system having two rings as described above, it is not preferable to employ the system due to the following disadvantages. One disadvantage is that when the shutter is charged in relation with the winding up of the film in a camera, it is required to arrange a linkage mechanism between the winding-up mechanism of the camera and the second ring in order to move the second ring to a starting position and thus the space within the camera is necessarily increased resulting in a relatively large size high cost camera. Another disadvantage is that both the first ring and the second ring encircle the photographing aperture resulting in an increase of the contact area of the first and second rings and also an increase of operational friction. Further, the component parts are made of larger size requiring more space and thus miniaturization and lightness in weight of the shutter cannot be obtained. A further disadvantage is that the inner diameter of the first ring for use in operating the sector is required to be a dimension of high accuracy and thus it is not possible to ignore the production cost of the component parts.